NTSB Identification: WPR09LA048
14 CFR Part 91: General Aviation
Accident occurred Tuesday, November 25, 2008 in Fillmore, UT
Probable Cause Approval Date: 06/11/2009
Aircraft: HUGHES 369HS, registration: N9154F
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
According to the pilot, during cruise flight the helicopter's engine lost power and it entered an autorotation. The helicopter was over mountainous/hilly terrain and there was no open place to land. The pilot selected a spot on a steep hill covered with 20- to 30-foot-tall oak trees. Upon touchdown, the helicopter began to roll, but was stopped by the vegetation. The tailboom incurred structural damage during the landing. Postaccident examination of the helicopter revealed that the fuel pump filter bowl's upper drain plug had been replaced with a non-standard threaded nipple fitting and cap. This cap was found with zero torque (loose) and partially backed off of its seat. Less than two threads retained the cap on its fitting. In standard configuration, the upper and lower drain plugs are lock-wired to each other, thus ensuring both fittings remain properly torqued. On the accident engine, the lower drain plug was lock-wired to the upper drain's threaded nipple fitting. However, the cap was not lockwired. The fuel spray nozzle's fuel supply line was found to be devoid of any residual fuel. (This line would typically have about 1 to 1.5 teaspoons of fuel following a normal engine shutdown.) The engine was removed from the airframe and shipped to the facilities of the engine manufacturer for a test run. The suspect loose cap was gently tightened with a wrench. The engine was then run and met all test cell parameters for new engine production. Since the fuel pump filter bowl operates at a negative pressure during operation, a compromise at this point in the fuel system would not result in a fuel leak, but would rather result in an air induction into the fuel system, interrupting the supply of fuel to the fuel spray nozzle.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The loss of engine power due to fuel starvation as a result of a loose fuel filter upper drain cap, which was not properly secured by maintenance personnel. Full narrative available
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